This invention is concerned with a gob distributor for a glassware manufacturing machine of the individual section type.
A glassware manufacturing machine of the individual section type comprises a plurality of independent glass manufacturing units, called "sections", each of which operates to manufacture gobs of molten glass into articles of glassware. The sections of a machine are arranged side-by-side on a common base to receive gobs from a common feeder. A gob distributor is positioned between the feeder and the sections to direct successive gobs received from the feeder to the sections in a predetermined sequence. The sections operate with phase differences between them so that, at any given time, each section is at a different stage of its operation from all the others.
The gob distributor of a machine of the individual section type comprises at least one gob-delivering scoop. There is one scoop for each gob delivered at a time and it is common practice for the feeder to deliver two or more gobs at a time and for the sections to each operate on a like number of gobs at a time. The scoop has an upper end portion arranged to receive gobs from the feeder, curves in a vertical plane, and is turnable about a vertical axis extending through the upper end portion thereof to align a lower end portion of the scoop with gob-delivering guides of the sections. The gob distributor also comprises moving means operable to turn the scoop about its vertical axis to align its lower end portion with the gob guides. Where there is more than one scoop, the moving means turns all the scoops about their respective axis to align the lower end portions of the scoops with respective sets of gob-delivering guides. The gob distributor also comprises control means operable to control the moving means so that the lower end portion of the scoop is moved into alignment with the gob-delivering guides of the sections in the predetermined sequence in timed relationship to the receipt of gobs by the upper end portion of the scoop so that the gobs are delivered to the sections in the predetermined sequence.
In a conventional gob distributor, the moving means comprises a ring-shaped gear through which an upper cylindrical portion of the scoop passes, the gear being mounted to turn about the vertical axis of the scoop and the scoop being mounted on the gear to turn therewith. The moving means also comprises a toothed rack meshed with the gear and movable longitudinally to cause the gear to turn through various angles and an electric motor operable to move the rack longitudinally thereof. The motor operates at a constant speed to rotate a cam which provides the control means of the distributor. The rack has a cam follower mounted thereon which is resiliently urged into contact with the cam. The shape of the cam determines the predetermined sequence and the precise alignments reached by the scoop.
The moving means and the control means of a conventional gob distributor are able to turn the scoop through the angles required with the precision necessary and sufficiently rapidly (as little as 0.15 seconds may be available for each turn). However, the control means is not adjustable in operation. Thus, when the mechanism wears to an extent that it lacks the necessary precision, the whole machine must be shut down for a considerable period to allow cam replacement. Furthermore, should one of the sections become inoperative, it is not possible to re-programme the distributor for less sections operating without replacing the cam. Cam replacement is rarely worthwhile when a section becomes inoperative and the normal procedure is to continue normal operation of the distributor but with an interceptor introduced between the feeder and the scoop to deflect the gobs that would otherwise be delivered to the inoperative section into a cullet chute. This procedure is wasteful in that the energy used to melt the deflected gobs is wasted and, furthermore, this procedure can be criticized on safety grounds as a failure of the interceptor could lead to a gob arriving at the inoperative section where a fitter may be working.
Various suggestions have been made concerning the provision of a gob distributor which can be re-programmed while the machine is in operation so that compensation for wear can be made and so that inoperative sections can be "programmed out". In one of these suggestions, see U.S. Pat. No. 4,357,157, the scoop is mounted on the output shaft of an electrical servo-motor which extends along the vertical axis. The servo-motor can be re-programmed by changing the electrical signals supplied thereto. This suggestion, however, requires the use of a heavy-duty electrical servo-motor, since the entire weight of the scoop is moved by the motor, which is expensive. Furthermore, where there are two or more scoops, a like number of servo-motors is required. In another suggestion, an electrical servo-motor is used to turn a worm which meshes with gears on which the scoops are mounted. This suggestion uses one servo-motor for all the scoops but requires a heavy-duty electrical servo-motor. Furthermore, it is believed that an electrical servo-motor driving a worm or a rack and pinion arrangement would not be able to position scoops sufficiently quickly to allow use of such a distributor with a machine having a large number of sections.
It is an object of the present invention to provide a gob distributor for a glassware manufacturing machine of the individual section type which can be rapidly re-programmed and which does not require the use of a heavy-duty electrical servo-motor.